(1) Field of the Invention
The present invention relates to photographic materials which comprise novel color photographic couplers.
(2) Description of the Prior Art
After a silver halide photographic material is exposed to light, when it is color-developed, the oxidized primary amine developing agent reacts with dye-forming couplers to form a color image. Generally, in this technique, color reproduction is effected by a substractive color process in which to reproduce blue, green and red, complementary color images of yellow, magenta, and cyan are formed.
As yellow dye image-forming agents, for example, acylacetanilide or benzoylmethane-type couplers are used., as magenta dye image-forming agents, for example, pyrazolone, pyrazolotriazole, pyrazolobenzimidazole, cayanozcetophenone or indazolone-type couplers are used; and as cyan dye forming agents, for example, phenol or naphthol-type couplers are used.
In multi-layer color photographic materials, to lessen color mixing, which the color reproduction, it is necessary to secure the couplers in their respective separate layers, thereby rendering them fast to diffusion. To render couplers fast to diffusion, many techniques have been used.
One method introduces a long-chained aliphatic group into the molecule of couplers to prevent diffusion. The couplers used in this technique are immiscible with aqueous gelatin solutions. Therefore, it is necessary, as disclosed in U.S. Pat. No. 2,322,027, that for the coating the couplers are dissolved in a high-boiling solvent and emulsified and dispersed into an aqueous gelatin solution.
However, in such a method, to improve the sharpness of the dye image by reducing the thickness of the coupler-containing layer, if the amount of a high-boiling organic solvent is decreased, the coupler is liable to crystallize out in the emulsion layer. It is therefore necessary to use a certain amount or more of a high-boiling organic solvent, and it is difficult to improve the sharpness of the dye image by sufficiently reducing the thickness of the coupler-containing layer. Further, if a high-boiling organic solvent is used, a large amount of gelatin is required because the coupler-containing layer is softened. As a result, the sharpness of the dye image degrades disadvantageously.
Other techniques to render couplers fast to diffusion include polymerizing the couplers. Known polymerizing polymers are lipophilic polymer couplers and hydrophilic polymer couplers.
A lipophilic polymer coupler may be prepared by emulsifying and dispersing a lipophilic polymer coupler dissolved in an organic solvent, obtained by the polymerization of a monomer coupler, into an aqueous gelatin solution to be made in the form of a latex, or it may be prepared directly by emulsion polymerization.
As a method to emulsify and disperse a lipophilic polymer coupler into an aqueous gelatin solution to be made in the form of a latex, use can be made of a method described in U.S. Pat. No. 3,451,820, and for emulsion polymerization, use can be made of methods described in U.S. Pat. Nos. 4,080,211 and 3,370,952.
However, when lipophilic polymer couplers are emulsified and dispersed into an aqueous gelatin solution to be made in the form of a latex, the coupler-containing layer is softened, similar to emulsification and dispersion, wherein a long-chain aliphatic group is introduced into the coupler molecule. As a result, a large amount of gelatin is required, thus increasing the thickness of the coupler containing layer. It is therefore difficult to adequately improve the sharpness of a dye image by using a lipophilic polymer coupler.
On the other hand, when using hydrophilic polymer couplers, since the hydrophilic polymer can be dispersed uniformly into a gelatin layer, the coupler-containing layer is less softened. It is therefore possible to decrease the thickness of the coupler layer by using a small amount of gelatin.
For example, polymer couplers that are prepared by joining reactive couplers to synthesized polymers (e.g., acrylic acid homopolymcrs and p-aminostyrene homopolymers) or natural high polymer compounds (e.g., gelatin) are described in U.S. Pat. Nos. 2,698,797, 2,852,381, 2,852,383, and 2,870,712, and Japanese Patent Publication Nos. 16932/1960 and 3661/1969, and polymer couplers that are prepared by copolymerizing couplers synthesized in the form of ethylenically-unsaturated monomers with other polymerizable monomers are disclosed in British Pat. Nos. 880,206, 955,197, 967,503, 967,504, 995,363, and 1,104,658. However, the above-described hydrophilic polymer couplers are not adequately fast to diffusion and they are also liable to allow colors to mix. Further, in the worst cases, the couplers disadvantageously flow out during the development processing. To overcome this, hydrophilic polymer couplers having phenolic hydroxyl groups or active methylene groups have been suggested in U.S. Pat. Nos. 4,207,109. 4,215,195, and 4,421,915, and Japanese Patent Application (OPI) No. 27139/1983 and 28744/1983. However, polymers of this type are still not adequately fast to diffusion, and the obtained dye images are low in density.